There are numerous standards for encoding numeric and other information in visual form, such as the Universal Product Codes (UPC) and/or European Article Numbers (EAN). These numeric codes allow businesses to identify products and manufactures, maintain vast inventories, manage a wide variety of objects under a similar system and the like. The UPC and/or EAN of the product is printed, labeled, etched, or otherwise attached to the product as a dataform.
Dataforms are any indicia that encode numeric and other information in visual form. For example, dataforms can be barcodes, two dimensional codes, marks on the object, labels, signatures, signs etc. Barcodes are comprised of a series of light and dark rectangular areas of different widths. The light and dark areas can be arranged to represent the numbers of a UPC. Additionally, dataforms are not limited to products. They can be used to identify important objects, places, etc. Dataforms can also be other objects such as a trademarked image, a person's face, etc.
Scanners that can read and process the dataforms have become common and come in many forms and varieties. One embodiment of a scanning system resides, for example, in a hand-held gun shaped, laser scanning device. A user can point the head of the scanner at a target object and press a trigger to emit a light beam that is used to read, for example, a dataform, on the object.
In an embodiment, semiconductor lasers are used to create the light beam because they can be small in size, they are low in cost and they do not require a lot of power. One or more laser light beams can be directed by a lens or other optical components along a light path toward an object that includes a dataform. The light path comprises a pivoting scan mirror that sweeps the laser light back and forth across the object and/or dataform. The mirror can be part of a scan motor comprising a spring, and a permanent magnet. The magnet is positioned in the vicinity of a drive coil, which oscillates the scan motor. There are numerous other known methods of sweeping the laser light, such as moving the light source itself or illuminating a plurality of closely spaced light sources in sequence to create a sweeping scan line. The scanner can also create other scan patterns, such as, for example, an ellipse, a curved line, a two or three dimensional pattern, etc.
The scanner also comprises a sensor or photodetector for detecting light reflected or scattered from an object and/or dataform. The returning light is then analyzed to obtain data from the object or dataform. Two known scan systems for collecting light are retroreflective scan systems and non-retroreflective scan systems.
In retroreflective scan systems, the same pivoting scan mirror that sweeps the laser light to form a scan line, also receives the light that returns to the scanner. The mirror's surface is made as large as possible to capture as much returning light as possible. The returning light is directed towards a sensor, such as for example, a photodiode, that emits electrical signals corresponding to the returning light. The returning light can be concentrated on the sensor using, for example, a parabolic shaped collection mirror, or in other embodiments the mirror can have a spherical or some other shape. Data is obtained from a targeted dataform by interpreting the electrical signals. The sensor can be relatively small since the field of view of the scanner is dynamic and the instantaneous field of view of the scanner is relatively small. An exemplary retroreflective scan system is described in U.S. Pat. No. 6,360,949, which is owned by the assignee of the instant invention and is incorporated by reference.
The performance of a retroreflective scan system is related to the scan system's collection area, i.e., the available area the scan system has to collect returning light. The more collection area the scan system has, the higher the scan system's performance will be. For example, a larger collection area can increase the range of the scan system and/or improve the scanning of lower contrast dataforms. The collection area for a scan system is determined by many factors including the area of the collection mirror, the area of the scan mirror, the angle of the scan mirror with respect to the front of the scan system, the size and location of the fold mirror, obstructions in the optical path, etc.
In non-retroreflective scan systems, the scan mirror that pivots to create a scan line is not used to receive light returning from a target dataform. Since the pivoting scan mirror does not have to receive returning light, it can be relatively small. Instead of using a large collection mirror and a small sensor to receive returning light, the scanner comprises a relatively large sensor that detects the returning laser light across its field of view. Since the field of view of the scanner is not dependant on the scan mirror, the sensor can be positioned below the source of the scan line. An exemplary non-retroreflective scan system is described in U.S. Pat. No. 6,592,040, which is owned by the assignee of the instant invention and is incorporated by reference.
Known non-retroreflective scan systems use scan motors created by an injection molding (IM) process, as described in U.S. Pat. No. 6,817,529, which is owned by the assignee of the instant invention and is incorporated by reference. In an exemplary embodiment, the scan motor comprises injection molded substrates and liquid injection molded (LIM) springs. The springs can be made of silicone, which provide shock protection. Additionally, the injection molded scan motor can be made at relatively low costs. Non-retroreflective scan systems are good candidates for injection molded scan motors because those systems use small mirrors, and small mirrors yield low inertia and low driving voltages. Since a retroreflective system uses a relatively large mirror, LIM scan motors have not been used since the drive voltages would be too high. Known retroreflective systems use scan motors that have springs made of mylar and/or metal. These materials do not have the cost and shock benefits of a material such as silicone.
Accordingly, there is a desire for a scan motor that can also be used in a retroreflective system that is durable, resistant to shocks and can be produced at low costs. Additionally, there is a desire for injection molded scan motors for non-retroreflective systems that use less power.
Although, retroreflective scan systems use collection mirrors that are relatively large, the overall volume of a retroreflective scan system can be very small, for example, 0.200 in3. A retroreflective scan system or more specifically a scan engine can be implemented as part of another device, such as, for example a handheld computer or handheld scanner. Since the devices that scan engines are found in are continuously shrinking, the scan engines included in the devices should be as small as possible, while providing adequate performance. In addition, it might not be possible to alter the shape of the scan engine to optimized internal volume, because an industry standard scan engine shape exists.
Because of the limited available volume, known small retroreflective scan engines might have sacrificed some collection area for other necessary features. For example, a relatively large scan motor, the angle of a scan mirror and/or the position of a fold mirror can reduce the collection area of a scan engine. Alternatively, a greater collection area might be obtained by optimizing or increasing the available internal area of a scan engine by changing its shape. Unfortunately, this may not be desirable since industry standards may exists with respect to the shape of a scan engine. Additionally, it is desirable for new scan engines to fit into existing devices.
Accordingly, there is a desire for a retroreflective scan system, with a large collection area, that can improve scan performance, reduce manufacturing costs and increase durability. Additionally, there is a desire for improvements in larger scan systems using designs developed for smaller scan systems.